Aircraft often fly at high altitudes, which are characterized by relatively low ambient pressures. To provide passengers with a pleasant environment, it is desirable to maintain aircraft cabin pressure (commonly referred to as “cabin pressure altitude”) within a relatively comfortable range during flight. This may be accomplished by controlling the rate at which air escapes from the aircraft's cabin utilizing one or more pressure outflow valves. Preferably, such outflow valves are relatively lightweight and compact, while at the same time being relatively durable and reliable. Furthermore, regulations require that such outflow valves employ redundancy features capable of mitigating single point failure situations, such as crack formation and propagation.
One known type of outflow valve that achieves the above-described goals comprises a non-metallic (e.g., plastic) flowbody having a flow passage therethrough, a rotatable shaft disposed in the flowbody, and a valve element (e.g., a butterfly valve plate) mounted on the shaft and disposed within the flow passage. The shaft is coupled to a valve actuator, which is, in turn, coupled to a controller. In response to commands from the controller, the actuator rotates the shaft to adjust the position of the valve and thereby control the rate of airflow through the flow passage. To reinforce the plastic flowbody and to provide the required redundancy, a metallic (e.g., aluminum) sleeve is disposed within the flow passage such that the sleeve's outer surface is substantially contiguous with the flowbody's inner surface thereby creating a dual-walled flow passage. The sleeve is coupled to the flowbody via an adhesive and a plurality of brackets and fasteners (e.g., rivets). The brackets may each be L-shaped and include-first and second openings therethrough. The first opening receives a first rivet that passes through (and thus couples) the flowbody and the sleeve, and the second larger opening receives a mounting bolt, which passes through a radial mounting flange provided around an end of the flowbody and through an aircraft support structure (e.g. a bulkhead) thereby attaching the flowbody and the sleeve to the aircraft's fuselage.
Although meeting many of the previously identified design goals, outflow valves of the type described are limited in certain respects. For example, as each bracket must be individually riveted, the production of such valves may be relatively time consuming and costly. Furthermore, the riveting process increases the risk of deforming the sleeve and of damaging (e.g., cracking) the plastic flowbody. Additionally, undue stress may be placed on the sleeve because the sleeve is not directly coupled to the support structure and because the riveted brackets do not evenly distribute the clamping force about the sleeve's circumference. Finally, the employment of multiple riveted brackets increases part count and negatively impacts the valve's appearance.
Considering the foregoing, it should be appreciated that it would be desirable to provide an outflow valve having a redundancy feature wherein the sleeve is secured to the flowbody without the use of multiple rivets or other such fasteners. It should also be appreciated that it would be desirable for such an outflow valve to utilize a sleeve attachment means that directly couples the sleeve to the support structure and that substantially evenly distributes the clamping force about the sleeve's circumference. Other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.